Allow each mod to have a default version

When a visitor arrives at the site for the first time, this will
ensure they have a certain set of mods on/off. Right now, that means
IC2-Classic is off by default, and everything else is on.

src/coffee/controllers/mod_pack_controller.coffee

@@ -6,7 +6,6 @@ All rights reserved.
 ###
 
 BaseController        = require './base_controller'
-{DefaultMods}         = require '../constants'
 {Duration}            = require '../constants'
 Mod                   = require '../models/mod'
 ModSelectorController = require './mod_selector_controller'